A telescope is an
instrument that is made to gather light. The more light it
gathers, the more powerful it is.

When a telescope is sold
by its magnification or power, they are cleverly avoiding the fact
that it has no light gathering ability. The power is
meaningless. The aperture or the size of the mirror is what
the scope is all about.

The three most popular
types of telescopes are Refractors, Newtonian Reflectors and Schmidt
Cassagrains.

Refractors use lenses to
collect light.

Newtonian Reflectors use
mirrors to collect light.

Schmidt Cassagrains and
Maksutov Cassagrains use both mirrors and lenses to collect light.

You can mount your
telescope on one of two different kinds of bases. A Dobsonian
(uses Alt/Az) or an Equatorial (uses RA/Dec).

A Dobsonian mount allows
you to move the telescope by hand. You can push, pull and
swing it in any direction.

An Equatorial mount
tracks objects in the sky using worm gears and electric computerized
motors.

Like microscopes,
telescopes use interchangeable eyepieces. The magnification of
an eyepiece changes what you see through the telescope. The
smaller the number, the closer you get.